DE112018007050B4 - Retroreflective window - Google Patents

Abstract

A retroreflective window (1, 2, 3) comprising: a first transparent sheet material (10a) and a second transparent sheet material (10b) arranged substantially parallel to each other; a transparent triangular prism (30) sandwiched between the first and second transparent sheet material (10a, 10b) and a first side (30a) along the first transparent sheet material (10a) in cross section and a second and a third side (30b, 30c) at an angle with respect to the first side (30a) having; anda changeover member (50) installed facing the second side (30b) which is a lower side of the second and third sides (30b, 30c) and between a reflective state in which a reflectance of visible light rays and infrared rays is 70 % or more, and a non-reflective state in which the reflectance of visible light rays and infrared rays is 30% or less, wherein when the switching element (50) is in the reflective state, in the triangular prism (30) ,a light beam incident on the first transparent plate material (10a) at an angle equal to or larger than a predetermined angle (a) with respect to a normal line (N) of the first transparent plate material (10a) and entering the triangular prism (30) of incident on the first side (30a), reflected from the changeover element (50) and the third side (30c), and then from the first transparent plate mat erial (10a) is emitted at the same angle as when entering, and light rays incident on the first transparent plate material (10a) at an angle to the normal line (N) smaller than the predetermined angle and entering the triangular prism ( 30) entering from the first side (30a), the light beam reaching the third side (30c) is transmitted and emitted from the second transparent plate material (10b).

Description

TECHNICAL AREA

The present invention relates to a retroreflective window.

STATE OF THE ART

Sunlight consists of about half visible light rays and about half infrared rays. Therefore, in order to suppress the need for cooling in summer, a window which cuts infrared rays while allowing visible rays of sunlight to pass through has been proposed. In order to lower infrared rays, there are a method of absorbing infrared rays and a method of reflecting infrared rays. However, in the former case, the window becomes hot and heat is radiated from the window, so the latter reflection method is effective. However, since the window, which simply reflects infrared rays, reflects the heat rays of sunlight coming from above downward, the ground in front of the building warms up, resulting in a heat island phenomenon.

For such a problem, a special film reflecting infrared rays upward (toward the sun) has been proposed (see Patent Literature 1). This film has an optical functional layer which reflects light rays in an infrared band and transmits light rays in a visible band, for example, in a zigzag cross-sectional shape. In this film, a visible light ray is transmitted through the optical functional layer and taken into space, and an infrared ray is reflected to the sunny side by the zigzag optical functional layer.

However, although the film described in Patent Literature 1 allows visible light rays to pass through and makes them visible to the scene outside the window, it also transmits visible light rays from the sun. Therefore, the film still requires a means of blocking direct rays of light, such as blinds.

Therefore, a selective transmission/reflection material has been proposed, which has a transparent portion which is inclined to totally reflect light beams having an incident angle of a predetermined value or more, and a mirror surface which is provided to reflect the light beam in an incident direction to reflect (see Patent Literature 2). According to this selective transmission/reflection material, a direct ray of light from the sun arriving at a predetermined angle of incidence or greater can be reflected to the sun side, and a ray of light arriving at an angle of incidence smaller than the predetermined value can be transmitted. Therefore, it eliminates the need for some other means of blocking the direct beam of light and ensures the view of the scene outside the window.

the US 2015/0285454 A1 describes a dynamic lighting control system. The dynamic light control system may include two or more handguards; one or more light redirecting elements disposed between the two or more boundary plates, the light redirecting elements comprising a deformable material; one or more fluid channels formed between the plurality of light redirecting elements and the two or more limiting plates; wherein the one or more light redirecting elements are arranged to deform relative to the position of the two or more restraining discs in response to one or more stimuli to allow redirection of light. A method of redirecting light may include introducing or removing a fluid into or from the one or more fluid channels.

the JP 2012-3024 A describes a window material having a first optical layer with an uneven surface, a wavelength-selective reflection layer formed on the uneven surface, and a second optical layer formed on the wavelength-selective reflection layer so that it fills the uneven surface. The wavelength-selective reflection layer selectively reflects light in a specific wavelength band while transmitting light other than the specific wavelength band, and the uneven surface has a variety of one-dimensional configurations.

the JP 2013-80142 A describes a light-shielding film. The light-shielding film consists of a prism sheet layer, a light-shielding layer and a filler layer, and the prism sheet layer is formed on the inner surface side with three-dimensionally shaped parts in which protrusions of triangular or trapezoidal columnar shape are arranged in parallel.

citation list

patent literature

• [Patent Literature 1]: JP 2014-142669 A
• [Patent Literature 2]: JP 2003-202159 A

SUMMARY OF THE INVENTION

Technical problem

However, since the selective transmission/reflection material described in Patent Literature 2 only reflects the direct light beam from the sun to the sunny side, it is preferable when a user does not want to let in the direct light beam. For example, if it is desired to let the direct light beam into the room to make the room brighter without using a lighting device, however, the direct light beam cannot be used. As a result, the usability of the direct light beam is reduced.

The invention has been accomplished to solve such a problem and an object thereof is to provide a retroreflective window which can block a direct light ray and reflect it to a sunny side while maintaining visibility and increase usability of the direct light ray.

the solution of the problem

A retroreflective window according to the invention is defined in claim 1 and comprises first and second transparent sheet materials, a transparent triangular prism located between the first and second transparent sheet materials, and a changeover element which changes between a reflective state and a non-reflective state can be. When the changeable element is in the reflective state, in the triangular prism, a light beam incident at a predetermined angle or greater is emitted from the first transparent plate material at approximately the same angle as when entering, and light beams incident at an angle smaller than the predetermined angle occurs, the light beam reaching the third side is transmitted and emitted from the second transparent plate material.

Advantageous Effects of the Invention

According to the invention, when the interchangeable element is in the reflective state, in the triangular prism, a light beam incident at a predetermined angle or greater is emitted from the first transparent plate material at approximately the same angle as when entering, after passing through the interchangeable element and the third side is reflected, and of light rays entering at an angle smaller than the predetermined angle, the light ray reaching the third side is transmitted and emitted from the second transparent plate material. Therefore, the direct ray of light from the sun can be reflected to the sunny side, and the ray of light such as the scene with an angle smaller than the predetermined angle can be captured. Furthermore, since the changeable element can be changed not only to the reflective state but also to the non-reflective state, not only the direct light beam is reflected to the sunny side but also the state can be changed to the non-reflective to increase the usability of the direct light beam. Therefore, it is possible to provide a retroreflective window capable of blocking the direct light ray and reflecting it to the sunny side while maintaining visibility and increasing the usability of the direct light ray.

character list

• 1 Fig. 12 is a schematic side view showing a retroreflective window according to a first embodiment of the invention.
• 2 12 is a perspective view showing the retroreflective window according to the first embodiment and showing a rotating mechanism.
• 3A until 3D 12 are conceptual diagrams showing optical paths of the retroreflective window according to the first embodiment, where 3A represents a first optical path, 3B represents a second optical path, 3C represents a third optical path, and 3D represents fourth and fifth optical paths.
• 4 12 is a schematic side view when the retroreflective window according to the first embodiment is rotated vertically.
• 5A until 5C 12 are conceptual diagrams showing optical paths when the retroreflective window according to the first embodiment is rotated vertically, where 5A represents a sixth optical path, 5B represents a seventh optical path, and 5C represents an eighth optical path.
• 6 14 is a diagram showing a relationship between an angle of a first base angle and a predetermined angle (rounded up by 1° unit) when a refractive index of the prism is changed when an apex angle of the prism is 25°.
• 7 is a diagram showing the relationship between the angle of the first base angle and the predetermined angle when the refractive index of the prism is changed, when the vertex angle of the prism is 30°.
• 8th Fig. 12 is a graph showing the relationship between the angle of the first base angle and the predetermined angle when the refractive index of the prism is changed when the vertex angle of the prism is 35°.
• 9 12 is a schematic side view showing a retroreflective window according to a second embodiment.
• 10 12 is a partial configuration diagram showing a retroreflective window according to a third embodiment.
• 11 Fig. 12 is a schematic side view showing an example when the retroreflective window is used for an inclined surface.

DESCRIPTION OF EMBODIMENTS

The invention is described below together with preferred embodiments. The invention is not limited to the embodiments described below, and can be modified as appropriate without departing from the gist of the invention. Further, in the embodiment described below, there is a part where illustration and description of a part of the configuration are omitted. However, regarding the details of the omitted technique, it goes without saying that a known or well-known technique is appropriately applied to the extent that there is no contradiction with the contents described below.

1 Fig. 12 is a schematic side view showing a retroreflective window according to a first embodiment of the invention. A retroreflective window 1 according to a 1 The illustrated example schematically comprises two transparent plate materials 10, a peripheral end member 20, a plurality of first prisms (triangular prisms) 30, a plurality of second prisms (second triangular prisms) 40, and a plurality of interchangeable elements 50.

The two transparent plate materials 10 are transparent plate materials arranged substantially parallel to each other. These transparent plate materials 10 are made of a glass material, for example. at a in 1 In the illustrated state, of the two transparent plate materials 10, a first transparent plate material 10a becomes the outside (area) side and a second transparent plate material 10b becomes the inside (area) side.

The peripheral end member 20 is interposed between the two transparent plate materials 10 at the peripheral end portions of the two transparent plate materials 10 . By providing the peripheral end member 20 at the peripheral end portions of the two transparent plate materials 10, an inner space closed by the two transparent plate materials 10 and the peripheral end member 20 is formed. In the embodiment, the internal space is in a vacuum state from the viewpoint of heat insulation, but not limited to this, it may be filled with a gas such as air, argon, or krypton.

The plurality of first prisms 30 are prisms (that is, a prism having a triangular prism shape) which are interposed between the first and second transparent plate materials 10a and 10b and each have a triangular shape in cross section. These first prisms 30 are arranged to face the first transparent plate material 10a such that a first side 30a is along the first transparent plate material 10a when viewed in cross section. Specifically, in the first embodiment, the first side 30a is provided in contact with the first transparent plate material 10a. A second side 30b and a third side 30c of the first prism 30 extend at a predetermined angle with respect to the first side 30a. The second side 30b is a side vertically below the third side 30c.

In the embodiment, the first prism 30 is made of a solid glass material or resin material. However, it is not limited to this and may be composed of a prism wall forming the outer wall of the first prism 30 and an inner member made of a transparent liquid sealed inside the prism wall. The inner member is not limited to a transparent liquid, and may be a transparent gel or solid. In addition, the first transparent plate material 10a can also serve as a part of the prism wall.

Each of the plurality of second prisms 40 is a prism (ie, a prism having a triangular prism shape) having a triangular shape in cross section, and has the same shape and refractive index as the first prism 30 . These second prisms 40 have a point-symmetrical orientation obtained by rotating the first prism 30 by 180°, and a second prism 40 is provided for each first prism 30 . Here, when only the first prism 30 is provided, light is refracted by the first prism 30 and the scene when it is viewed from the inside of the room side is distorted. However, since the second prism 40 is provided as a pair with the first prism 30, distortion of the scene when viewed from the inside of the room is suppressed (an image restoration effect is provided). The second prism 40 may be formed of a prism wall and an inner member, similar to the first prism 30, or may be formed of a solid member.

Specifically, the second prisms 40 are arranged to face the second transparent plate material 10b such that fourth sides 40a of the second prisms 40 are along the second transparent plate material 10b. A fifth side 40b and a sixth side 40c of the second prism 40 extend at a predetermined angle with respect to the fourth side 40a. Fifth side 40b is vertically above sixth side 40c. In such a second prism 40, the sixth side 40c faces the third side 30c of the first prism 30, which is adjacent in the horizontal direction, and the fifth side 40b faces the second side 30b of the first prism 30, which is adjacent in the vertical direction is adjacent, facing.

The plurality of changeover elements 50 are elements arranged to face the second side 30b of the first prism 30 and can change state between a reflective state and a non-reflective state. The changeover element 50 has a visible light and infrared ray reflectance of 70% or more in the reflective state, and a visible light and infrared ray reflectance of 30% or less in the non-reflective state.

Specifically, in the first embodiment, in the changeover member 50, a surface is a reflection layer 51 having a reflectance of visible light and infrared rays of 70% or more, and is provided in contact with the second side 30b of the first prism 30. On the other hand, the other surface (the back surface side of the reflection layer 51) of the changeover element 50 is an absorption layer 52 having an absorption rate of visible light and infrared rays of 70% or more, and is opposed to the fifth side 40b of the second prism 40 with a space therebetween.

Also, in the embodiment, the second prism 40 is arranged with a minute gap between the first prism 30 and the second transparent plate material 10b. Intermediate assembly elements such as minute columns and particles are placed between them to keep a minute gap. As a result, the retroreflective window 1 has a laminated structure of the first prism 30, the intermediate arranging element, the second prism 40, the intermediate arranging element and the second transparent plate material 10b in this order, and even when the internal space is in a vacuum state, it becomes supported to withstand the pressure.

2 14 is a perspective view showing the retroreflective window 1 according to the first embodiment, showing a rotating mechanism. In the following description, a structure (two transparent plate materials 10, peripheral end members 20, first prism 30, second prism 40 and changeover member 50) excluding a rotating mechanism 60 in the retroreflective window 1 is referred to as a laminated body (flat plate body) L.

As in 2 shown, the retroreflective window 1 includes the rotation mechanism 60 in addition to the laminated body L. The rotation mechanism 60 includes a hinge 61, a window frame 62 and a locking means (not shown), and can rotate in the vertical direction while the left and right positions of the laminated body L can be maintained.

Specifically, the hinge 61 is a rotary shaft member provided at the center of the left and right sides of the laminated body L extending vertically. The window frame 62 is a rectangular frame member into which the laminated body L is fitted, and is provided at the center of the left and right sides with a rotation hole (not shown) into which the hinge 61 is inserted while extending vertically. A locking means (not shown) serves to fix the laminated body L in a state where the laminated body L is fitted into the window frame 62 .

With such a configuration, a user can release the locking means and rotate the stacked body L around the hinge 61 . After the rotation, a user locks and fixes the laminated body L to the window frame 62 by the locking means. In this way, the laminated body L can be rotated vertically about the hinge 61, and at the time of rotation, it is possible to perform vertical rotation where the relative positions of one plate member 10a and the other plate member 10b are switched while left and right Positions of the laminated body L are maintained.

Here, in the embodiment, the first prism 30 has a refractive index and each interior angle of a triangle set so that the following optical paths OP1 to OP5 can be realized. 3A until 3D 12 are conceptual diagrams showing the optical paths OP1 to OP5 of the retroreflective window 1 according to the first embodiment, where 3A represents the first optical path OP1, 3B represents the second optical path OP2, 3C represents the third optical path OP3, and 3D represents the fourth and fifth optical paths OP4 and OP5.

Of the first through fifth optical paths OP1 through OP5, the first through third optical paths OP1 through OP3 are optical paths for a light beam incident on the first transparent plate material 10a when an angle (i.e., elevation angle when it is used in an upright position) with respect to a normal line N of the first transparent plate material 10a is a predetermined angle α or larger, and enters the triangular prism 30 from the first side 30a.

As in 3A 1, the first optical path OP1 is an optical path where a light beam entering at a predetermined angle α or larger first reaches the second side 30b is totally reflected (70% reflection or more) by the reflection layer 51, the third side 30c, and is totally reflected by the third side 30c (theoretical total reflection), and then the light beam is emitted from the first transparent plate material 10a toward the sun side at an angle α1', which is substantially the same as an approach angle a1 .

As in 3B 1, the second optical path OP2 is an optical path where a light beam entering at a predetermined angle α or greater first reaches the third side 30c is totally reflected (theoretical total reflection) at the third side 30c, the second side 30b and is totally reflected (70% reflection or more) by the reflection layer 51, and then the light beam is emitted from the first transparent plate material 10a toward the sunny side at an angle α2' which is substantially the same as an approach angle α2 .

As in 3C As shown, the third optical path OP3 is an optical path where an incoming light beam first reaches the third side 30c, is totally reflected at the third side 30c (theoretical total reflection), reaches the first side 30a, is totally reflected at the first side 30a (theoretical total reflection), reaches the second side 30b, and is totally reflected (reflection of 70% or more) at the reflection layer 51, and then the light beam is totally reflected at the first side 30a and the third side 30c (theoretical total reflection) and is emitted from the first transparent plate material 10a toward the sun side at an angle α3' which is substantially the same as an approach angle α3.

In order to realize such first to third optical paths OP1 to OP3, the angle of incidence of the first and second optical paths OP1 and OP2 to the third side 30c must be equal to or larger than a critical angle. Furthermore, the angle of incidence of the third optical path OP3 on the first and third sides 30a and 30c must be equal to or larger than the critical angle.

As in 3D shown, the fourth and fifth optical paths OP4 and OP5 are optical paths for a light beam incident on the first transparent plate material 10a when the elevation angle (e.g. angles α4 and α5) is smaller than the predetermined angle α and into the triangular prism 30 enters from the first side 30a. The first prism 30 completely transmits (theoretical total transmission) a light beam reaching the third side 30c among the light beams entering at an elevation angle smaller than the predetermined angle α, and emits the light beam through the second transparent plate material 10b (see 1 ). In this case, the angle of incidence of the fourth and fifth optical paths OP4 and OP5 on the third side 30c must be smaller than the critical angle.

4 12 is a schematic side view when the retroreflective window 1 according to the first embodiment is rotated vertically. As in 4 shown when the laminated body L is rotated vertically, the second prism 40 has a refractive index and internal triangle angles set so as to realize optical paths OP4 to OP8 described below. Of these, the fourth and fifth optical paths OP4 and OP5 are the same as those described with reference to FIG 3A until 3D are described, so that the description thereof is omitted.

5A until 5C 12 are conceptual diagrams showing optical paths OP6 to OP8 when the retroreflective window 1 according to the first embodiment is rotated vertically, where 5A represents a sixth optical path OP6, 5B represents a seventh optical path OP7, and 5C represents an eighth optical path OP8. All of the sixth to eighth optical paths OP6 to OP8 are optical paths for a light beam incident on the second transparent plate material 10b when an angle (i.e. elevation angle when used in an upright position) with respect to the normal line N of the second transparent plate material 10b is a predetermined angle α or larger, and in das second triangular prism 40 enters from the fourth side 40a.

As in 5A As illustrated, the sixth optical path OP6 is an optical path where a light beam entering at a predetermined angle α or larger reaches the fifth side 40b, is emitted from the fifth side 40b, and reaches the absorption layer 52.

As in 5B 1, the seventh optical path OP7 is an optical path in which a light beam entering at a predetermined angle α or greater first reaches the sixth side 40c is totally reflected (theoretical total reflection) at the sixth side 40c, the fifth side 40b, is emitted from the fifth side 40b and reaches the absorption layer 52.

As in 5C 1, the eighth optical path OP8 is an optical path where a light beam entering at a predetermined angle α or greater first reaches the sixth side 40c is totally reflected (theoretical total reflection) at the sixth side 40c, the fourth side 40a is reached, is totally reflected at the fourth side 40a (theoretical total reflection), reaches the fifth side 40b, and is emitted from the fifth side 40b to reach the absorption layer 52.

In order to realize such sixth to eighth optical paths OP6 to OP8, the incident angle of the sixth optical path OP6 to the fifth side 40b needs to be smaller than the critical angle. Further, the angle of incidence of the seventh optical path OP7 to the sixth side 40c must be equal to or larger than the critical angle, and the angle of incidence of the seventh optical path OP7 to the fifth side 40b after total reflection must be smaller than the critical angle. Furthermore, the angle of incidence of the eighth optical path OP8 on the sixth side 40c must be equal to or larger than the critical angle, and the angle of incidence on the fourth side 40a after total reflection must be equal to or larger than the critical angle, and further the angle of incidence must be the fifth side 40b must be smaller than the critical angle after total internal reflection.

Here, when the laminated body L is rotated vertically, the sixth to eighth optical paths OP6 to OP8 reach the absorption layer 52, so that the interchangeable element 50 is efficiently heated by the direct rays of light. When the exchangeable element 50 is heated, as in 4 1, the first prism 30 which is in contact with the changeover member 50 is also heated, and the first transparent plate material 10a which is in contact with the first prism 30 is also heated. Therefore, the first transparent plate material 10a can be heated to bring about a heating effect on the interior side.

The first prism 30 and the second prism 40 have the same refractive index and the same shape. Therefore, if the prisms 30 and 40 described below are adopted, the first to eighth optical paths OP1 to OP8 described above can be realized.

In the following description, the angle (the angle formed by the fourth side 40a and the sixth side 40c) formed by the first side 30a and the third side 30c is referred to as an apex angle AA ( please refer 1 ), and the angle (the angle formed by the fifth side 40b and the sixth side 40c) formed by the second side 30b and the third side 30c is referred to as a first base angle BA1 ( please refer 1 ), and further, the angle (the angle formed by the fourth side 40a and the fifth side 40b) formed by the first side 30a and the second side 30b is referred to as a second floor angle BA2 (see 1 ).

6 13 is a diagram showing a relationship between the angle of the first base angle BA1 and the predetermined angle α (rounded up by 1° unit) when the refractive index of the prisms 30 and 40 is changed when the apex angle AA of the prisms 30 and 40 is 25° amounts to.

As in 6 shown when the material of the prisms 30 and 40 is a porous material with a refractive index of 1.17 when the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° the predetermined angle α 41°.

When the material of the prisms 30 and 40 is a porous material having a refractive index of 1.25, when the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75°, the predetermined one is Angle α 37°.

When the material of the prisms 30 and 40 is a porous material with a refractive index of 1.30, when the first base angle BA1 is 105° and 75°, the predetermined angle α is 41°, and when the first base angle BA1 is 100°, 95 °, 90°, 85° and 80°, the predetermined angle α is 34°.

When the material of the prisms 30 and 40 is fluororubber having a refractive index of 1.33 and sealed water, when the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order , the predetermined angle α is 44°, 37°, 33°, 33°, 33°, 37° and 44°.

When the material of the prisms 30 and 40 is a fluorine resin with a refractive index of 1.37 and 20% saline filled therein when the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75 ° is in this order, the predetermined angle α is 49°, 41°, 33°, 31°, 33°, 41° and 49°.

If the material of the prisms 30 and 40 is acrylic with a refractive index of 1.41 and silicon included, if the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order , the predetermined angle α is 54°, 45°, 37°, 30°, 37°, 45° and 54°.

If the material of the prisms 30 and 40 is borosilicate glass with a refractive index of 1.48, if the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order, the predetermined angles α 65°, 53°, 44°, 35°, 44°, 53° and 65°.

If the material of the prisms 30 and 40 is soda-lime glass with a refractive index of 1.52, if the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order, the predetermined angles α 73°, 58°, 48°, 38°, 48°, 58° and 73°.

If the material of the prisms 30 and 40 is polycarbonate with a refractive index of 1.59, if the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order, the predetermined angles α NG (NG means a value of 90° or more, which is a value that makes no sense in the product. Hereinafter the same applies.), 70°, 56°, 45°, 56°, 70° and NG .

Here, since the smaller the predetermined angle α is, the more direct light rays from the sun can be reflected to the sun side over a wider angular range and the more they can be guided to the absorbing layer 52, the smaller predetermined angle α is preferable. On the other hand, it is desirable that the window has a small apex angle AA, a wide vertical spacing between the changeover elements 50, and an outside scene to be projected into the room. Therefore, it is desirable that a minimum predetermined angle α is set with respect to a certain apex angle AA, and the predetermined angle α appropriately covers the altitude range of the sun considering time and season in the installation area and direction. Furthermore, as in 6 shown, when the refractive index is about 1.41 and the first base angle BA1 is 90°, the predetermined angle α has the minimum value (30°). Therefore, it can be said that the prisms 30 and 40 preferably have a refractive index of about 1.41 and the first base angle BA1 of 90°. However, due to the problem of the material of the prisms 30 and 40, the prisms 30 and 40 may not have a refractive index of about 1.41 and the first base angle BA1 of 90°, and the refractive index and the internal angle may be set so that the predetermined angle α is realized up to the minimum value of the predetermined angle α + 10° (40°).

That is, at the in 6 illustrated example, when the first base angle BA1 is 75° or larger and 105° or smaller at the refractive index of 1.25, the first base angle BA1 is 80° or larger and 100° or smaller at the refractive indexes of 1.30 and 1.33 is, the first base angle BA1 is 85° or larger and 95° or smaller at the refractive indexes of 1.37 and 1.41, and the first base angle BA1 is 90° at the refractive indexes of 1.48 and 1.52, the be predetermined angles α 40 ° or smaller, it is preferred.

In the embodiment, the prisms 30 and 40 are not limited to those in which the refractive index and internal angle are set so that the predetermined angle α of the minimum value of the predetermined angle α + 10° is realized. For example, to realize the first to eighth optical paths OP1 to OP8 described above, when the apex angle AA is 25°, the refractive index must not be 1.59 or more and the first base angle BA1 must not be 105° or more and 75° or be smaller. That is, the prisms 30 and 40 are in the altitude range of the altitude range that the sun can take considering the time and season in the installation area and direction, the refractive index and the angle can be set so that the first to eighth optical Paths OP1 to OP8 can be realized. The prisms 30 and 40 are not limited to the case where the refractive index and the angle are set so that the first to eighth optical paths OP1 to OP8 are realized in the entire high altitude range of the sun. The refractive index and the angle may be set so that the first to eighth optical paths OP1 to OP8 are realized only in a part (for example, the highest altitude in the installation area) of the altitude range that the sun can occupy.

Here puts 6 represents the predetermined angle α when the vertex angle AA is 25°, but when the angle of the vertex angle AA changes, the value of the predetermined angle α also changes.

7 is a table showing the relationship between the angle of the first base angle BA1 and the predetermined angle α when the refractive index of the prisms 30 and 40 is changed when the apex angle AA of the prisms 30 and 40 is 30°.

As in 7 shown, when the material of the prisms 30 and 40 is a porous material with a refractive index of 1.17, the predetermined angle α is 35° when the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, is 80° and 75°.

When the material of the prisms 30 and 40 is a porous material having a refractive index of 1.25, when the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75°, the predetermined one is Angle α 30°.

When the material of the prisms 30 and 40 is a porous material having a refractive index of 1.30, when the first base angle BA1 is 105° and 75°, the predetermined angle α is 33°, and when the base angle BA1 is 100°, 95° , 90°, 85° and 80°, the predetermined angle α is 27°.

When the material of the prisms 30 and 40 is fluororubber having a refractive index of 1.33 and including water, when the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order , the predetermined angle α is 37°, 29°, 26°, 26°, 26°, 29° and 37°.

When the material of the prisms 30 and 40 is a fluorine resin with a refractive index of 1.37 and 20% saline filled therein when the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75 ° is in this order, the predetermined angle α is 41°, 33°, 26°, 24°, 26°, 33° and 41°.

If the material of the prisms 30 and 40 is acrylic with a refractive index of 1.41 and silicon included, if the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order , the predetermined angle α is 45°, 37°, 29°, 22°, 29°, 37° and 45°.

If the material of the prisms 30 and 40 is borosilicate glass with a refractive index of 1.48, if the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order, the predetermined angles α 53°, 44°, 35°, 27°, 35°, 44° and 53°.

If the material of the prisms 30 and 40 is soda-lime glass with a refractive index of 1.52, if the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order, the predetermined angles α 58°, 48°, 38°, 30°, 38°, 48° and 58°.

When the material of the prisms 30 and 40 is polycarbonate with a refractive index of 1.59, the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order is the predetermined one Angle α 70°, 56°, 45°, 35°, 45°, 56° and 70°.

Thus, even when the apex angle AA is 30°, when the refractive index is about 1.41 and the first base angle BA1 is 90°, the predetermined angle α has the minimum value (22°). Therefore, when the apex angle AA is 30°, it is preferable to set the refractive indexes and the internal angles of the prisms 30 and 40 so that the predetermined angle α is 32° or smaller.

8th 12 is a diagram showing the relationship between the angle of the first base angle BA1 and the predetermined angle α when the refractive index of the prisms 30 and 40 is changed when the apex angle AA of the prisms 30 and 40 is 35°.

As in 8th shown when the material of the prisms 30 and 40 is a porous material with a refractive index of 1.17 when the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° the predetermined angle α 29°.

When the material of the prisms 30 and 40 is a porous material having a refractive index of 1.25, when the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75°, the predetermined one is Angle α 23°.

When the material of the prisms 30 and 40 is a porous material having a refractive index of 1.30, when the first base angle BA1 is 105° and 75°, the predetermined angle α is 27°, and when the base angle BA1 is 100°, 95° , 90°, 85° and 80°, the predetermined angle α is 21°.

When the material of the prisms 30 and 40 is fluororubber having a refractive index of 1.33 and including water, when the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order , the predetermined angle α is 29°, 22°, 19°, 19°, 19°, 22° and 29°.

When the material of the prisms 30 and 40 is a fluorine resin with a refractive index of 1.37 and 20% saline filled therein when the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75 ° is in this order, the predetermined angle α is 33°, 26°, 19°, 17°, 19°, 26° and 33°.

If the material of the prisms 30 and 40 is acrylic with a refractive index of 1.41 and silicon included, if the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order , the predetermined angle α is 37°, 29°, 22°, 14°, 22°, 29° and 37°.

If the material of the prisms 30 and 40 is borosilicate glass with a refractive index of 1.48, if the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order, the predetermined angles α 44°, 35°, 27°, 19°, 27°, 35° and 44°.

If the material of the prisms 30 and 40 is soda-lime glass with a refractive index of 1.52, if the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order, the predetermined angles α 48°, 38°, 30°, 22°, 30°, 38° and 48°.

If the material of the prisms 30 and 40 is polycarbonate with a refractive index of 1.59, if the first base angle BA1 is 105°, 100°, 95°, 90°, 85°, 80° and 75° in this order, the predetermined angles α 56°, 45°, 35°, 27°, 35°, 45° and 56°.

In this way, even if the apex angle AA is 35°, the predetermined angle α has the minimum value (14°) when the refractive index is about 1.41 and the first base angle BA1 is 90°. Therefore, when the apex angle AA is 30°, it is preferable to set the refractive indexes and the internal angles of the prisms 30 and 40 so that the predetermined angle α is 24° or smaller.

Next, the operation of the retroreflective window 1 according to the embodiment will be explained with reference to FIG 1 until 5C described.

First, in the retroreflective window 1 according to the embodiment in which Fig 1 shown state, the in the 3A until 3D illustrated, first to fifth optical paths OP1 to OP5 are realized by setting the refractive index and the internal angle of the first prism 30.

That is, the light beam entering the first prism 30 at the predetermined angle α or larger with respect to the first transparent plate material 10a forms the first to third optical paths OP1 to OP3, is transmitted through the first transparent plate material 10a in im Emits at essentially the same angle as when entering, and is not reflected to the ground side.

Further, part of the light rays entering the first prism 30 at the smaller angle than the predetermined angle α with respect to the first transparent plate material 10a forms the fourth and fifth optical paths OP4 and OP5. Therefore, of the light beams entering the first prism 30 at an angle smaller than the predetermined angle α, the light beam reaching the third side 30c is totally transmitted and emitted from the second transparent plate material 10b to the interior side.

Further, of the light beams entering the first prism 30 at the angle smaller than the predetermined angle α, the light beam reaching the second side 30b undergoes total reflection (total reflection at the reflective layer 51) or total transmission, and a part of they are emitted to the indoor side and the rest are emitted to the outside of the room.

Furthermore, it is assumed that the 2 The rotating mechanism 60 shown in FIG. In this case, in the retroreflective window 1, the second prism 40 is on the outside side as shown in FIG 4 shown. In this state, the retroreflective window 1 realized in the 3A until 3D illustrated fourth and fifth optical paths OP4 and OP5 and in the 5A until 5C shown sixth to eighth optical paths OP6 to OP8.

That is, light rays entering the second prism 40 at the predetermined angle α or greater with respect to the second transparent plate material 10b form the sixth to eighth optical paths OP6 to OP8, and sunlight can be collected in the absorption layer 52. As a result, the light beams can heat the first transparent plate material 10a through the first prism 30, so that it is possible to provide the heating effect on the indoor side.

Further, part of the light rays entering the second prism 40 at an angle smaller than the predetermined angle α with respect to the second transparent plate material 10b forms the fourth and fifth optical paths OP4 and OP5. Therefore, the light rays entering the second prism 40 at the predetermined angle α or smaller are totally transmitted and emitted from the first transparent plate material 10a to the indoor side unless blocked by the changeover member 50 .

In the first embodiment, since the changeover member 50 is in contact with the first prism 30 and the first prism 30 is in contact with the first transparent plate material 10a, the method of heating the first transparent plate material 10a using that collected in the absorbing layer 52 to sunbathe accepted. However, the invention is not limited to this, and the heat medium can be circulated in the absorbing layer 52, and the heat medium can be heated and used in other devices or the like. In this case, the interchangeable member 50 and the first prism 30 need not be in contact with each other, and the first prism 30 and the first transparent plate material 10a need not be in contact with each other.

In this way, according to the retroreflective window 1 according to the embodiment, when the changeover member 50 is in the reflective state, the first prism 30 brings a light beam incident at the predetermined angle α or greater thereto emitted from the first transparent plate material 10a are, by the reflection at the changeover element 50 and the third side 30c at approximately the same angle as entering, and of the light rays entering at an angle smaller than the predetermined angle α, the light ray which reaches the third side 30c , transmitted and emitted from the second transparent plate material 10b. Therefore, the direct light beam from the sun can be reflected to the sun side, and the light beam such as the scene at an angle smaller than the predetermined angle α can be captured. Further, since the changeable element 50 can be changed not only to the reflective state but also to the non-reflective state, not only the direct light beam is reflected to the sunny side, but also the reflective state can be changed to the non-reflective state to improve the usability of the increase direct light rays. Therefore, it is possible to provide the retroreflective window 1 capable of blocking the direct light ray and reflecting it to the sunny side while maintaining the visibility and increasing the usability of the direct light ray.

Moreover, the rotation mechanism 60 allowing the laminated body L having the first prism 30 and the like to rotate in the vertical direction is provided and the changeover member 50 has the reflection layer 51 and the absorption layer 52, and thus rotation changes over by the rotation mechanism 60 the state between a reflection state and an absorption state. Therefore, the rotation mechanism 60 can switch the state between the state in which the direct light beam is blocked and reflected to the sunny side and the state in which the direct light beam is absorbed and used for indoor heating or the like. As a result, the usability of direct light beams can be increased.

Next, a second embodiment of the invention will be described. The retroreflective window according to the second embodiment is similar to that of the first embodiment, but a part of the configuration is different. In the following description, elements that are the same as or similar to those in the first embodiment are given the same reference numerals and characters, and description thereof is omitted.

9 12 is a schematic side view showing a retroreflective window according to the second embodiment. As in 9 1, the changeable element 50 in a retroreflective window 2 according to the second embodiment is constituted by an element which can be changed between an opaque reflection state and a transparent non-reflection state (transmission state) depending on a temperature environment, a light irradiation environment, or a stressing state. Therefore, in the second embodiment, when the interchangeable element 50 becomes opaque and is in a reflective state, the direct light ray is reflected to the sunny side, and when it becomes transparent and is in a non-reflective state, the direct light ray can be taken to the indoor side will. Further, in the following description, the transmissive state is described as the non-reflective state. However, it is not necessarily limited to the permeable state and may be in the absorbent state.

Specifically, the changeable element 50 is made of a material such as thermochromic, photochromic, electrochromic, and the like that changes color when exposed to high temperatures, irradiation with ultraviolet rays, or the like, or a component such as electronic paper. For example, "umglass," which is a type of electrochromic, becomes transparent when a voltage is applied and becomes opaque and reflects light rays when a voltage is not applied. Furthermore, the electronic paper can be used by many technologies, for example, a magnetophoretic black-and-white alternating display type.

Furthermore, the changeover member 50 is not limited to the above material, and may be formed of a transparent tube and a specific liquid. Here, some liquids with lower critical solution temperature (LCST) properties become transparent below the phase separation temperature and become cloudy above the phase separation temperature (cloud point). For the For example, an aqueous N-isopropylacrylamide solution has a cloud point near body temperature, below which it has a transmittance of about 100%, and above which it has a transmittance of about 0%. Therefore, such a liquid can be sealed in a transparent tube to form the changeover member 50 .

Next, the operation of the retroreflective window 2 according to the second embodiment will be described.

First, in the retroreflective window 2 according to the second embodiment, it is assumed that the changeover member 50 becomes cloudy and is in a reflective state. In this case, the light rays entering the first prism 30 at the predetermined angle α or greater with respect to the first transparent plate material 10a are emitted through the first transparent plate material 10a at substantially the same angle as the approach angle and do not become too reflected from the bottom side as in the first embodiment.

Furthermore, even for light rays entering the first prism 30 at an angle smaller than the predetermined angle α with respect to the first transparent plate material 10a, the light ray reaching the third side 30c is fully transmitted and separated from the second transparent one Plate material 10b emitted to the indoor side.

On the contrary, it is assumed that the changeover element 50 becomes transparent and is in a non-reflective state. In this case, when light rays entering the first prism 30 at the predetermined angle α or greater with respect to the first transparent plate material 10a reach the changeover element 50, the light rays pass through the changeover element 50 and are reflected from the second transparent plate material 10 b emitted to the indoor side through the second prism 40 . Therefore, by using the direct rays of light, it is possible to bring the lighting effect into the room.

Further, the light rays entering the first prism 30 at an angle smaller than the predetermined angle α are also emitted from the second transparent plate material 10b to the interior side.

In this way, according to the retroreflective window 2 according to the second embodiment, similarly to the first embodiment, it is possible to provide the retroreflective window 2 which can block the direct ray of light and reflect it to the sunny side while maintaining visibility, and the can increase the usability of direct light rays.

Furthermore, since the changeover element 50 is formed of an element which changes a state between the cloudy reflection state and the transparent non-reflection state depending on the temperature environment or the stressing state when it becomes cloudy, the direct light beam can be blocked and reflected to the sunny side , and when it becomes transparent, the direct ray of light can be taken into the room. Therefore, the usability of the direct light rays can be improved.

Next, a third embodiment of the invention will be described. A retroreflective window according to the third embodiment is similar to that of the first embodiment, but a part of the configuration is different. In the following description, elements that are the same as or similar to those in the first embodiment are given the same reference numerals and characters, and description thereof is omitted.

10 12 is a partial configuration diagram showing a retroreflective window 3 according to the third embodiment. In addition, in 10 the changeover member 50 as viewed from the stacking direction of the laminated body L is shown. As in 10 1, the retroreflective window 3 according to the third embodiment includes operating mechanisms 70 and 80 for changing a state of the changeable element 50 between a reflective state and a non-reflective state. Also, in the third embodiment, an example will be described in which the two operating mechanisms 70 and 80, that is, the first operating mechanism 70 and the second operating mechanism 80, are provided. However, the retroreflective window 3 according to the third embodiment may have only one of the operating mechanisms 70 and 80 .

First, in the third embodiment, the changing member 50 includes a transparent hollow member 53 and is capable of changing a state between a reflective state in which a white or silver liquid is sealed in the hollow member 53 and a non-reflective state in which a transparent liquid is enclosed. With such a changeover member 50, the transparent liquid can be introduced from one end side of the hollow member 53, and the white or silver liquid can be introduced from the other end side. The exchange element 50 is with a jelly-like gel block 54 for separating the two liquids within the hollow member 53 is provided.

The first operating mechanism 70 is for changing the state of the changeover element 50 between the reflective state and the non-reflective state by a user operation and includes an upper pulley 71, a lower pulley 72, a ladder cord 73, an operating portion 74, a plurality of liquid storage containers 75 and a plurality of flexible tubes 76.

The upper pulley 71 and the lower pulley 72 are pulley members provided on an upper side and a lower side of the retroreflective window 3 . The ladder cord 73 is an endless cord member wrapped around the upper sheave 71 and the lower sheave 72 . An operating section 74 and a plurality of liquid storage containers 75 are attached to the ladder cord 73 .

The operating portion 74 includes, for example, an inner magnet 74a and an outer magnet 74b. The inner magnet 74a is a magnet member arranged in the inner space formed by the two plate members 10 and the peripheral end member 20 and connected to the conductor cord 73 . The outer magnet 74b is attracted to the inner magnet 74a via the second transparent plate material 10b located on the inner area side. The inner magnet 74a and the outer magnet 74 are formed of strong magnets such as neodymium magnets.

A plurality of liquid storage tanks 75 are arranged vertically along a ladder string 73 extending vertically, and the liquid storage tank 75 is a tank which stores a transparent liquid. The liquid storage tanks 75 are provided in the same number as the changeover members 50, and each liquid storage tank 75 is connected to one end of each changeover member 50 through the flexible pipe 76 having flexibility.

The second operation mechanism 80 is for automatically changing the state of the changeover member 50 between the reflective state and the non-reflective state regardless of a user's operation. The second operating mechanism 80 includes a cord member 81, a weight W, a shape memory alloy spring 82, a grease case 83, a heat transfer grease G, a plurality of liquid storage tanks 84, and a plurality of flexible tubes 85.

The cord member 81 is a cord member where an upper end is attached to a triangular projection P protruding from the first transparent plate material 10a, and the weight W is attached to a lower end. The shape memory alloy spring 82 is a member that can expand or contract depending on the ambient temperature. The shape memory alloy spring 82 is interposed between the cord members 81 and housed in the grease case 83 . The inside of the grease case 83 is filled with the heat transfer grease G. Further, the grease case 83 is provided in contact with a transparent plate material 10a.

A plurality of liquid storage containers 84 are arranged vertically along the vertically extending cord member 81, and the liquid storage container 84 is a container storing white or silver liquid. The same number of liquid storage tanks 84 as the number of changeover members 50 are provided, and each liquid storage tank 84 is connected to the other end of each changeover member 50 through the flexible pipe 85 having flexibility.

Next, the operation of the retroreflective window 3 in the third embodiment will be described. First, it is assumed that the outside temperature is high in summer. In this case, the outside air temperature is transmitted from the first transparent plate material 10a to the shape memory alloy spring 82 through the grease case 83 and the heat transfer grease G, and the shape memory alloy spring 82 is in a stressed state. When the shape memory alloy spring 82 is in a state of tension, the string member 82 is pulled up and the plurality of liquid storage containers 84 are also pulled up.

When a user moves up the outer magnet 74b of the operating portion 74 in this state, the plurality of liquid storage containers 75 move down through the ladder cord 73 . As a result, the position of the liquid storage container 84 in which the white or silver liquid is stored is raised and the position of the liquid storage container 75 in which the transparent liquid is stored is lowered.

Therefore, the white or silver liquid of the liquid storage container 84 pushes the gel block 54 toward the one end side, and the interchangeable member 50 is in a reflective state. When the changeover element 50 is in the reflective state, the direct light becomes ray is reflected to the sunny side as in the first and second embodiments.

On the other hand, it is assumed that the outside temperature is low in winter. In this case, the outside air temperature is transmitted from the first transparent plate material 10a to the shape memory alloy spring 82 through the grease casing 83 and the heat transfer grease G, and the shape memory alloy spring 82 is in a relaxed state. When the shape memory alloy spring 82 is in the relaxed state, the cord member 81 is lowered and the positions of the plurality of liquid storage tanks 84 are also lowered.

When a user moves down the outer magnet 74b of the operating portion 74 in this state, the plurality of liquid storage containers 75 move up through the ladder cord 73 . As a result, the position of the liquid storage container 84 storing the white or silver liquid is lowered and the position of the liquid storage container 75 storing the transparent liquid is raised.

Therefore, the transparent liquid of the liquid storage tank 75 pushes the gel block 54 to the other end side, and the interchangeable member 50 is in a non-reflective state. When the changeover element 50 is in the non-reflective state, the direct light beam is taken into the indoor side as in the second embodiment.

In this way, according to the retroreflective window 3 according to the third embodiment, similarly to the first embodiment, it is possible to provide the retroreflective window 3 which can block the direct ray of light and reflect it to the sunny side while maintaining visibility, and the can improve usability of the direct light beam.

Further, according to the third embodiment, the changeover member 50 is formed by the transparent hollow member 53 and can change a state between the reflective state in which the white or silver liquid is sealed and the non-reflective state in which the transparent liquid is sealed. Therefore, the direct ray of light can be blocked and reflected to the sunny side when the white or silver liquid is enclosed, and the direct ray of light can be taken into the space when the transparent liquid is enclosed. Therefore, the usability of the direct light beam can be improved.

The invention is described above based on the embodiments. However, the invention is not limited to the above embodiments, and modifications can be made without departing from the gist of the invention, and other techniques can be appropriately combined within a possible range. Furthermore, known or well-known techniques can be combined within a possible range.

For example, in the embodiments, examples are described in which the retroreflective windows 1 to 3 are used for the upright surface, but the retroreflective windows 1 to 3 can be used not only for the upright surface but also for an inclined surface (for example, a roof surface). be used. 11 Fig. 12 is a schematic side view showing an example in which the retroreflective windows 1 to 3 are used for an inclined surface. As in 11 1, the retroreflective windows 1 to 3 can be used, for example, in an inclined surface that inclines toward the north side in Japan. This is because even in such a case, the optical paths OP1 to OP8 and the like can be realized from the relation with the predetermined angle during elevation.

In the above-described embodiments, the retroreflective windows 1 to 3 have a two-layer structure of the first transparent plate material 10a and the second transparent plate material 10b, but may have a transparent plate material having a three or more layer structure.

Further, in the second embodiment, the opaque reflection state and the transparent non-reflection state are switched. However, the invention is not limited to this, and may be configured to change a state between a clouded reflection state and a blackened absorption state (absorption rate of 70% or more). In this case, the changeover member 50 may be formed of a component such as magnetophoretic electronic paper. In this example, similarly to the first embodiment, the interchangeable element 50 is brought into contact with the second prism 40, or the heating medium is heated by using the interchangeable element 50 in such a manner that the direct light beam is converted into heat and then into the space can be taken.

Similarly, the third embodiment can be configured to have a state between the reflek animal state in which a white or silver liquid is filled and the absorbent state (absorption rate of 70% or more) in which a black liquid is filled. In this case, the liquid container 84 is filled with a black liquid.

Although various embodiments are described above with reference to the drawings, it goes without saying that the invention is not limited to such examples and various changes or modifications can be made within the scope of the claims. Furthermore, the basic elements in the above-described embodiments can be arbitrarily combined within the scope of the claims.

Reference List

1 to 3

retroreflective window

10a

first transparent sheet material

10b

second transparent sheet material

30

first prism (triangular prism)

30a

first page

30b

second page

30c

third page

40

second prism (second triangular prism)

40a

fourth page

40b

fifth page

40c

sixth page

50

interchangeable element

51

reflective layer

52

absorption layer

53

hollow element

60

rotation mechanism

L

laminated body (flat plate)

N

normal line

OP1 to OP8

first to eighth optical paths

a

predetermined angle

Claims (4)

Retroreflective window (1, 2, 3), with: a first transparent plate material (10a) and a second transparent plate material (10b) arranged substantially parallel to each other; a transparent triangular prism (30) which is arranged between the first and the second transparent plate material (10a, 10b) and has a first side (30a) along the first transparent plate material (10a) in cross section and a second and a third side (30b, 30c) at an angle with respect to the first side (30a); and a changeover member (50) installed facing the second side (30b) which is a lower side of the second and third sides (30b, 30c), and between a reflective state in which a reflectance of visible light rays and infrared rays is 70 % or more and a non-reflective state in which the reflectance of visible light rays and infrared rays is 30% or less, wherein when the interchangeable element (50) is in the reflective state, in the triangular prism (30), a light beam incident on the first transparent plate material (10a) at an angle equal to or greater than a predetermined angle (a) with respect to a normal line (N) of the first transparent plate material (10a) and entering the triangular prism (30) from the first side (30a), reflected by the changeover element (50) and the third side (30c), and then emitted by the first transparent sheet material (10a) at the same angle as when entering, and of light beams incident on the first transparent plate material (10a) at an angle to the normal line (N) smaller than the predetermined angle and entering the triangular prism (30) from the first side (30a), the light beam, reaching the third side (30c) is transmitted and emitted from the second transparent plate material (10b). Retroreflective window (1) after claim 1 , further comprising: a transparent second triangular prism (40) having the same shape as the triangular prism (30) in cross section, a fourth side (40a) in contact with the second transparent plate material (10b), and fifth and sixth sides ( 40b, 40c) at an angle with respect to the fourth side (40a), and arranged to be point symmetrical to the triangular prism (30); and a rotating mechanism (60) capable of rotating in a vertical direction while left and right positions of a flat plate body (L) having the first and second transparent plate materials (10a, 10b), the triangular prism (30), the second triangular prism (40) and the exchange element (50) are maintained, where the changeover element (50) comprises, a reflection layer (51) which is provided in contact with the second face (30b) of the triangular prism (30) and has a reflectance of visible light rays and infrared rays of 70% or more, and an absorption layer ( 52) which is provided on a back surface of the reflection layer (51) spaced from the fifth face (40b) of the second triangular prism (40), and has an absorption rate of 70% or more of visible light rays and infrared rays, and rotation by the rotation mechanism (60) changes a state between the reflective state and the non-reflective absorbing state. Retroreflective window (2) after claim 1 , wherein the changeover element (50) is formed of an element which can change a state between an opaque reflective state and a transparent non-reflective state depending on a temperature environment, a light irradiation environment or a stress application state, or an element which a state between a clouded reflection state and a blackened non-reflection state by a magnetophoretic process. Retroreflective window (3) after claim 1 , wherein the changing member (50) is formed of a transparent hollow member (53) and for changing a state between the reflective state in which a white or silver liquid is filled, and the non-reflective state in which a transparent liquid or a filled with black liquid.

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